Study on the Properties of Nano-CeO₂/Polyurea-Based Gel Grease for Electric Motor Bearings

In response to the harsh operating conditions of high-speed, high-temperature bearings in new energy vehicle drive motors, this study focuses on enhancing the performance of polyurea-based gel greases through the use of nano-additives. Using polyurea-based gel grease as the matrix, nano-composite gel greases with different CeO₂ loadings were prepared, and their tribological properties and rheological behavior were characterized using four-ball friction tests, rheological testing, and SEM analysis. The results indicate that adding 0.5 wt% CeO₂ increased the grease's yield stress by approximately 75.4% and significantly raised its apparent viscosity. This rheological enhancement effect may be attributed to the physical adsorption of ultrafine particles onto the polyurea fiber network and potential interfacial interactions between the particles and the fiber surfaces. Compared to the original grease, the average coefficient of friction decreased by 10.4%, and the average wear scar diameter decreased by 12.7%. Meanwhile, the shear stress increased by 110.41 Pa, and the viscosity increased by 1102 Pa·s. This study provides experimental evidence and technical references for the development of high-performance gel lubricants suitable for motor bearings operating under high-temperature conditions.